One known type of information storage device is a disk drive device that uses magnetic media to store data and a movable read/write head that is positioned over the media to selectively read data from or write data to the media.
FIG. 1a illustrates a typical disk drive device 2. A magnetic disk 201 is mounted on a spindle motor 202 for spinning the disk 201. A voice coil motor arm 204 carries a head gimbal assembly (HGA) 200 that includes a slider 203 incorporating a read/write head and a suspension 213 to support the slider 203. A voice-coil motor (VCM) 209 is provided for controlling the motion of the motor arm 204 and, in turn, controlling the slider 203 to move from track to track across the surface of the disk 201. In operation, a lift force is generated by the aerodynamic interaction between the slider 203 and the spinning magnetic disk 201, such that the voice coil motor arm 204 maintains a predetermined flying height above the surface of the magnetic disk 201.
FIG. 1b shows a perspective view of the slider shown in FIG. 1a, and FIG. 1c shows a top plan view of the slider shown in FIG. 1b. As illustrated, the slider 203 comprises a leading edge 219 and a trailing edge 218 opposite to the leading edge 219. Four electrical connection pads 215 are provided on the trailing edge 218 for electrically connecting the slider 203 to the suspension 213 (as shown in FIG. 1a). The trailing edge 218 also has a pole tip 216 formed thereon which incorporates a magnetic read/write head (not shown) on its central position for achieving reading/writing operation with respect to the disk 201. The pole tip 216 is formed on the trailing edge 218 by suitable manner such as deposition. In addition, an air bearing surface pattern 217 is formed on one surface of the slider 213 perpendicular to both the leading edge 219 and the trailing edge 218.
As shown in FIG. 1d, the pole tip 216 has a layered structure and comprises from top to bottom a second inductive write head pole 116, a first inductive write head pole 118 spacing away from the second inductive write head pole 116, a second shielding layer 111 and a first shielding layer 113. All above components are carried on a ceramic substrate 122. The pole tip 216 is used for achieving data reading/writing operation. A magneto-resistive element (MR element) 112, along with a lead layer 114, which is disposed at two lateral sides of the MR element 112 and electrically connected to the MR element 112, is provided between the first shielding layer 113 and the second shielding layer 111. Referring to FIG. 1e, a set of copper coils 117 is provided between the second inductive write head pole 116 and the first inductive write head pole 118 for assisting in writing operation. In addition, an overcoat 115 consisting of a silicon layer 12 and a diamond-like carbon (DLC) layer 13 disposed on the silicon layer 12 is covered on the surface of the pole tip and surface of the ceramic substrate 122 to protect the slider.
In structure of above slider, a GMR (giant magneto-resistive) element is normally used as a read element to achieve data reading operation. However, with continuously increasing demand of a hard disk drive (HDD) of a higher recording density, current application of GMR element has almost gotten to its extreme limit. As a result, a new MR element such as a tunnel magneto-resistive (TMR) element, which can achieve higher recording density than a GMR element, is developed to replace the GMR element.
Referring to FIG. 1f, a conventional TMR element 10 comprises two metal layers 11 and a barrier layer 14 sandwiched between the two metal layers 11. The overcoat 115 consisting of a silicon layer 12 and a DLC layer 13 disposed on the silicon layer 12 is covered on the surface of the metal layers 11 and the barrier layer 14 to protect the TMR element 10.
In manufacturing process of a slider, the magneto-resistive resistance (MRR) value of a TMR element must be controlled to be higher than a predetermined value so as to maintain good flying dynamic performance for the slider. For example, in lapping process of a slider, the TMR element should be precisely lapped in order to adjust the MR height thereof to a designed value, since the MR height has great influence on the MRR value, thus further influencing the dynamic performance of the slider. Take another example, in vacuum process of the slider, the MR height should be kept constant all the time so that the MRR is unchanged.
However, in conventional TMR element structure, since metal layers are in direct contact with the silicon layer of the overcoat, the metal material of the metal layers readily diffuses into the silicon layer, and the metal material diffused into the silicon layer itself forms electrically conductive lead, which electrically connects the two metal layers together, thus a shunting path for circuitry of the TMR element being formed. The shunting path results in reduction of the MRR value of the TMR element, and consequently, degrades dynamic performance of the slider and read/write performance of the HDD. It is proved by experiment that after an overcoat is covered on the surface of the TMR element in a vacuum process, the MRR drop is about 4%, and sometimes the MRR drop can even dramatically rise to 10%, which is fatal to dynamic performance of the slider.
Therefore, there is a need for an improved design to overcome the prior art drawbacks.